1. Field of the Invention
The present invention is directed to the use of an enzyme for the manufacture of an agent for the treatment and/or prophylaxis of a bacterial infection.
2. Discussion of Background Information
The farming of many different types of animals is important throughout the world for the production of food for human consumption. When the animals are reared, they come into contact with a variety of infection-causing bacteria, such as Campylobacter and Salmonella. In some cases these bacteria may spread directly from animals to humans (zoonosis). Accordingly, it is necessary from an economic, environmental and health perspective that such bacterial infection is prevented or eradicated in the animal prior to human consumption to prevent the spread of the disease to humans.
The domestic animal of particular, but not exclusive, concern with regard to zoonosis is the chicken. Campylobacter and Salmonella are particularly prevalent in the chicken. The bacteria are transmitted to the bird in a variety of ways, including through feed, water, litter and vermin. The bacteria initially infect the caecae of the chicken. The disease then progresses to the small intestine where infestation may cause loss of weight in the bird. A particular problem with the chicken is that it is almost impossible to eviscerate in a sterile manner with the result that bacteria inhabiting the intestines will invariably be transmitted to the saleable carcass. Accordingly the potential for zoonosis is great, unless the carcass is handled or cooked properly. The cost of human infection caused by eating improperly treated chicken is significant in terms of both time and lives.
Accordingly, presently there is a demand for improved methods of reducing bacterial infection in animals such as the chicken, in particular those intended for human consumption.
Various solutions to the problem of bacterial infection have been proposed. Current methods of control include the application of antibiotics, feed sterilisation and careful and controlled handling and cooking of the carcass after slaughter. Feed sterilisation has proved ineffective in the absence of a sterile rearing environment (which is impractical) whilst controlled handling and cooking cannot be relied upon in every instance. The application of antibiotics has proved unpopular with consumer groups wishing to reduce the quantity of potentially harmful chemicals in food. The use of antibiotics has the additional problem that if they are not introduced into the animal in a properly controlled manner, antibiotic-resistant strains of bacteria can be created, making such infections more difficult to treat in the future. The prophylactic use of antibiotics in animal feed has thus been regulated in some countries (notably Sweden and Finland) effectively reducing the available methods of control. Indeed no single method provides a barrier which completely prevents bacteria being transferred from the animal to humans.
As an alternative to the above methods it has been proposed in Poultry Science, 1994 73:402–407, to introduce flora into chickens to compete with the bacteria causing the infection. Such mucosal competitive exclusion flora (MCE) were found to reduce the level of Campylobacter jejuni infection in chickens. However, the competitive exclusion treatment is not found to be consistently effective, its efficacy varying from animal to animal.
JP-A-81-73055 discloses animal feeds intended to prevent contamination with Salmonella. The feeds are indicated to contain partially decomposed mannan in the form of mannose polysaccharides. These are produced by degradation of mannan with an enzyme, produced by micro-organisms. The resulting feed was found to be moderately effective against Salmonella in chickens, but is not effective against Campylobacter. 
U.S. Pat. No. 5,124,262 discloses a mannose isomerase enzyme used for converting fructose to mannose. The mannose thus produced is taught to be useful in feeds, for inhibiting the growth of Salmonella in chickens.
In Bamboo J. 1993, pp. 29–35, xylan prepared from steamed bamboo grass is mentioned as inhibiting the growth of various human intestinal bacteria. In particular the xylan is indicated to be effective against Salmonella. However, the inhibition effect is reversed after a period of 24 hours.
The above methods have proved more desirable from an environmental and health point of view, than the administration of antibiotics. However, none have proved effective enough to be commercially viable.
WO 93/01800 discloses the use of a protease for the preparation of a medicament effective against intestinal pathogens in animals. The pathogens of interest include Campylobacter. However, there is no mention of enzymes other than proteases being useful in controlling animal pathogens.
EP-A-0 681 787 discloses use of a carbohydrase or protease for the manufacture of an agent for the treatment of Coccidiosis. However, Coccidiosis in chickens is caused by protozoal oocytes. The document does not indicate how bacterial pathogens in chickens, or other animals, can be controlled.